The present invention relates to a programmable digital arithmetic circuit, particularly, a Programmable Digital Arithmetic IC (PDIC). The PDIC of this invention has a large benefit when used as an arithmetic system such as various simulators and a programmable digital control board (a substrate having a dedicated transmission function by programming the standard substrate offline).
When an operational amplifier, resistor and capacitors are appropriately combined and wired, depending on the difference in the combinations and wiring, it is possible to realize a variety of basic analog arithmetic circuits that carry out specific mathematical operations. In addition, when each of the basic analog arithmetic circuits are converted to a digital circuit by applying Kirchhoff""s law, it is possible to realize basic digital arithmetic circuits that are equivalent to each basic analog arithmetic circuit. These digital arithmetic circuits are comprised of an adder (adding circuit), coefficient unit (coefficient circuit), and integrator (integrator circuit). The above has already been demonstrated in U.S. Pat. No. 6,003,054 (hereinafter referred to as xe2x80x9c""054 patentxe2x80x9d)). Moreover, a digital arithmetic circuit comprising an adder, coefficient unit and integrator can constitute a digital polyarithmetic IC that can selectively constitute said variety of different basic digital arithmetic circuits by changing the coefficient value of the coefficient unit, namely, a general-purpose digital arithmetic IC that can select from a multiplicity of operational functions. In addition, by extending and connecting the multiplicity of above-mentioned general-purpose digital arithmetic ICs in a crisscross pattern, it is possible to constitute the desired digital arithmetic circuit. This fact also has been discussed in ""054 patent.
A microprocessor, DSP (Digital Signal Processor) and DDA (Digital Differential Analyzer) are examples of digital arithmetic ICs. These are sequential processing types based on the Neumann Computer and software interferes with the operational process, consequently, it is difficult to increase the speed of the operational process.
The present invention is to further develop the technological philosophy of the PDIC described in ""054 patent, and to contrive a circuit structure so that it is clear and easy to use by the users of a PDIC. In other words, the PDIC described in ""054 patent was not easy to handle for users because changing the functions and settings of the coefficients was realized through the setting of the coefficient value. In this invention, the change in the functions and settings of the coefficients of the PDIC are separated. Changing the functions is realized by a matrix switches and during the setting of the coefficients a purely physical coefficient value can be chosen so that a PDIC circuit that can be easy to understand and handle, for users will be constituted. In addition, in the present invention, the number of coefficient units in the PDIC is reduced by using a matrix switches so that the circuit size of the entire PDIC is reduced and consequently an inexpensive PDIC is constituted.
In order to solve the above-mentioned problems, the present invention is constituted such that each input/output terminal of the element circuit such as an integrator, differentiator, adder and coefficient unit are connected to each other via a matrix switches. By selectively turning on and off each switching element of said matrix switches, the necessary digital arithmetic circuit is selectively constituted. In other words, a matrix switches is added to the digital arithmetic IC as a circuit structure control element (circuit selection control element) for the digital arithmetic circuit, and during the selection of the digital arithmetic circuit with the desired operational functions, without relying on the coefficient value of the coefficient unit, the necessary digital arithmetic circuit is selectively constituted by selectively turning on and off the switching elements of the matrix switches.
If the number (type) of the functions desired for the PDIC is finite, the intersections that need to be turned on and off from among all the intersections of the matrix on the matrix switches are limited. Therefore, the PDIC is completed by arranging the switching elements only at the necessary intersections.